The interiors of most van-type vehicles have a front row of seats for the van driver and a passenger and a large compartment in the rear of the vehicle for additional seating, for cargo storage or both. Often a sliding door is provided on one or both sides of the van to access the interior compartment.
Van side doors may be power operated to open and close the same. EP 0122556 discloses a power operated door that is moved between opened and closed positions by a motor mounted on the door that powers a drive gear engaged with a gear track or rack on the vehicle body. The gear is mounted near the lower edge of the door and the motor is mounted in close proximity to the drive gear. The motor is rotationally coupled to the drive gear by a relatively short, rigid drive shaft and a gear train.
Placing the drive motor and associated drive structures that cooperate with the motor to drive the door adjacent the drive gear greatly limits the amount of space available for the drive gear, the motor, and the cooperating drive structures. Because the space available for the motorized drive system is limited at areas adjacent the drive gear, it would be necessary in EP 0122556 to limit the size of the drive system components, including the motor and drive gear. This creates other problems. For example, a small drive gear limits the range of stacked tolerances that can be provided by the drive system between the drive gear and rack. This increases automobile manufacturing difficulties, and results in noisy gear meshing when the door is moving, and increases mechanical wear on the teeth of the drive gear. In addition, limiting the size of the motor limits the power that can be provided for moving the door and restricts the manufacturer to using relatively small motors with a relatively short service life compared to a larger motor.
Power operated doors must also be able to operate in manual mode. When the power operated sliding door of EP 0122556 is operated in manual mode, the drive gear is engaged with the rack on the vehicle and the shaft of the motor is engaged with the drive gear so that the motor shaft rotates when the door is moved manually. This back-driving of the motor during manual door opening and closing is undesirable because it causes unnecessary wear on the motor and makes moving the door more difficult for the user.